1. Field
The present invention relates to sharpening an image and, more particularly, to adaptively sharpening local image content of an image.
2. Background Information
In digital imaging systems, image sharpening, sometimes referred to as xe2x80x9ccrispening,xe2x80x9d is employed to enhance the image by removing the blurring effect introduced, typically, by different signal processing and/or optical filtering operations. A variety of xe2x80x9csharpening kernelsxe2x80x9d are typically employed in this process. Usually this involves applying a convolution of the sharpening kernel with the blurred image. One approach is to apply a fixed kernel to sharpen an image or set of images. Another approach is to allow the sharpness to be modified based on human judgement. For example, the Photoshop(copyright) software product available from Adobe Systems, Inc., employs this latter approach. However, a fixed kernel does not produce good results in some situations, such as where the image characteristics are varying, and manual adjustment is not practical in some situations, such as where video is being employed. A need, therefore, exists for a process or technique that at least in part addresses the foregoing shortcomings.
Briefly, in accordance with one embodiment of the invention, a method of sharpening an image includes the following. A crispening parameter is adaptively computed for a local region of a captured image based, at least in part, on a measure of the local contrast and the local brightness. A kernel is applied to the local region of the captured image using the adaptively computed crispening parameter.